Heretofore, as a method to make the surface of metals, ceramics, glass, plastics, synthetic fibers, paper and like materials hydrophilic, silicon surface active agents, polyethylene glycol surface active agents, poly(hydroxylethyl metacrylate) surface active agents, polyvinyl alcohol coatings, various anti-static additives including anionic surface active agents, cationic surface active agents, non-ionic surface active agents and ampholytic surface active agents were applied to the surface.
Polyester, nylon, polyolefin, acrylic like synthetic fibers and rayon fibers like artificial fibers can be used in various industries for use in clothing, commercial and retail use, construction and resin reinforcement. Especially, synthetic fibers can be used due to lightness, strength, relatively low-price and variety of coloring. In these industries, refining the surface of synthetic fibers is often required. Applying a hydrophilic adsorbed film is one of the methods for refining the surface.
For example, a feature of clothing such as underwear, sportswear and socks made of polyester, nylon, acrylic and like synthetic fibers is that it does not absorb water or moisture, which makes it possible to manufacture light weight clothing. However, since most synthetic fibers except vinylon are hydrophobic, they have some problems such as being uncomfortable when wearing due to low sweat absorbency and low permeability. In order to solve the problems, many attempts have been made. One method is to deform the fiber section. Another way is to coat a surface active agent on the surface. Another way is to manufacture the fabric structure, nit fabrication, and sewing design in various ways.
Also, a further problem is that such fibers are easily electrically charged and tend to stick to the body due to water-repellency. In order to alleviate the problem, some methods have been taken, which add fiber treatment agents or spray anti-charging agents on the fibers.
Also, a highly hydrophilic property is useful for industrial use. For example, if a fishing net is highly hydrophilic, it sinks into the water quickly. In another example, if the surface of synthetic fibers is highly hydrophilic when strengthening the resin, adhesion between the fiber and resin will be improved. A highly hydrophilic property is also required when strengthening the adhesion to the surface of cement, concrete and like materials. It is also required to make the surface of synthetic fibers of towels, sanitary products, diaper, sanitary napkin and like products hydrophilic.
However, the conventional methods aforementioned have a serious problem in which surface active agent molecules and coating material molecules do not bond covalently to the surface of a substrate, which causes poor durability. Especially, since improvement in sweat absorbency and permeability is limited in clothings, further development is needed.